UV Nanosecond Lasers
The most common medium for laser micromachining is Nd:YVO4 operating at 355nm wavelength. The UV laser is generated using two non-linear optics that convert the wavelength from 1064nm to 532nm, and then from 532nm to 355nm. During each conversion step some power and pulse energy are lost in the process, typically around 50%. Therefore a 1064nm laser at 20W will provide around 7W at 355nm. The UV laser technology is extremely mature and has been used in the industrial marketplace for many years for a wide variety of machining and marking applications. As with any frequency converted laser the non linear crystals used for the conversion are consumables but last a long time with typical lifetimes in the 8-10,000 hour range. This lifetime period is only used when the laser is firing. The schematic drawing shows a highly simplified version of the elements for wavelength conversion for a UV nanosecond laser. Aside from the laser medium and non linear crystals the other major component is the Q switch that directly controls the pulse frequency, and indirectly controls the pulse width that the laser produces at a certain frequency. Lower frequencies provide shorter pulse (ultrashort pulse laser) duration, typically around 20ns at 30 kHz, rising to 100ns at 200 kHz.